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000
FXUS65 KGJT 121752
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1152 AM MDT Fri Apr 12 2024

.KEY MESSAGES...

- Unseasonably warm, dry and breezy today.

- Scattered light showers tonight through Saturday morning over
  the the San Juan and central Colorado mountains.

- Active weather returns Monday through Wednesday as a pair of
  Pacific storms impact the region bringing showers, cooler
  temperatures and accumulating mountain snow.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 341 AM MDT Fri Apr 12 2024

Skies were clear over the forecast area beneath the transitory
ridge over the Rockies early this morning. Meanwhile, a closed
mid-level low pressure system was digging southward over the
eastern Pacific off the coast of Oregon/northern California.

The eastern Pacific low continues to drift south this morning
according to model consensus, then turns southeastward later
today forcing the axis of the high pressure ridge to shift east
of the Continental Divide by 00Z/Sat. As the ridge shifts east,
a short wave trough in the southwesterlies aloft combined with
jet divergence deliver a modest slug of mid-level moisture to
the southern half of the forecast area. Models suggest enough
lift and instability for showers, but the dry sub-cloud layer
hints at mainly virga, and this confined to the southern and
central Colorado mountains this afternoon. Meanwhile, deep
mixing will bring breezy southwest winds from late morning
through the afternoon which will be enhanced by virga.

The short wave trough pushes northeastward across the forecast
area tonight bringing increased clouds and scattered showers
over the San Juan and central Colorado mountains. Precipitation
amounts are expected to be light as evaporation in the sub-
cloud layer remains a factor. The short wave trough moves east
of the Divide Saturday morning and a few showers may linger
across the north-central and northern Colorado mountains after
sunrise. Dry weather is expected to return during the remainder
of the day on Saturday, though the ECMWF suggested instability
showers are a possibility along the Park Range and Flat Tops
during the afternoon. Should this occur, this activity should
be fairly isolated in coverage.

Afternoon highs are expected to climb to around 15 degrees above
normal this afternoon as southwesterly flow aloft advects
warmer air into the region. Increased clouds overnight will
hinder cooling overnight, so lows on Saturday morning should
also run well above normal. Slightly cooler air arrives on
Saturday as the high pressure ridge retreats farther east and
the eastern Pacific low moves to the San Francisco Bay area
late in the day. As a result, the area will see temperatures
dip a bit with highs around 3 to 5 degrees cooler than those
forecast for today.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 341 AM MDT Fri Apr 12 2024

Gusty breezes diminish late Saturday evening, giving way to
quiet yet continued mild weather overnight. The Pacific storm,
having already made landfall earlier in the day on Saturday,
will continue its slow march eastward across the Great Basin on
Sunday. Out ahead of this system, another day of warm, dry, and
breezy weather is in store thanks to the strengthening southwest
flow in between the closed low to our west and the ridge to our
east. Dry low levels, deep mixing, and modestly strong winds
aloft will support wind gusts in excess of 30 to 40 mph across
eastern Utah and western Colorado with 50+ mph gusts not ruled
out. High temperatures will once again be well into the 70s to
near 80 for the lower desert valleys, into the 60s for the
higher valleys, and into the 50s for mountain towns... which is
10 to 15 degrees above normal overall.

By Monday morning, the deep closed low will be on our doorstep
and is currently progged to track due east across our CWA over
the course of the day. Increasing moisture and forcing
associated with the low and along a cold front will bring fairly
widespread precipitation across the mountains but not much in
the adjacent lower valleys. Snow levels between 7000 and 8000
feet will support snow in the mountains, but accumulating snow
will mostly be confined above 9000 to 10000 feet given the mild
antecedent air mass in place. Overall, snowfall amounts continue
to look sub-advisory. Behind the front, much cooler air will
filter in from the west, resulting in highs 10 to 15 degrees
cooler than on Sunday.

After the low departs into the central Plains, wrap around
moisture and orographic lift within northwesterly flow will
keep snow showers going across the central and northern Colorado
mountains through Tuesday morning before tapering off during
the afternoon. In the wake of the low, shortwave ridging briefly
builds in and brings drier and milder air to the region which
will especially be felt in the lower elevations. Then attention
quickly turns to another large trough and closed low which will
be dropping out of western Canada and into the northern Rockies
and northern Plains Tuesday into Wednesday. The latest models
continue to trend farther north with the low`s evolution with
less impacts this far south. As of now, it seems the central and
northern Colorado mountains have the best chance to be clipped
with some additional shower activity Wednesday into Thursday,
but that`s no guarantee. Outside of those mountains, it seems
like most everywhere else has better odds to stay mainly dry,
but breezy given the tightening pressure gradient. Either way,
the cooler and near average temperatures are likely to stick
around through the long term period under fairly persistent
northwest flow.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1152 AM MDT Fri Apr 12 2024

Winds become breezy this afternoon from the southwest ahead of a
disturbance that will also bring increasing SCT to BKN cloud
cover late this afternoon or early this evening through Saturday
morning with clearing skies after 12Z Saturday. Isolated to
scattered virga showers will accompany this disturbance but TAF
sites are not expected to be directly impacted by showers, but
rather gusty winds from nearby virga. VFR conditions will
prevail through the TAF period with CIGS staying above ILS
breakpoints.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...NL
LONG TERM...MDM
AVIATION...MDA